Power transmission, conveyor and vehicle track

ABSTRACT

A belt having a joint with abutting ends both above and below the neutral axis of longitudinal bending of the belt, and a flexible jointing ply located between the abutting ends and lying along the neutral axis to reinforce the joint, the flexible jointing ply being of a strength sufficient to withstand substantially the same tensile load as that which the uncut belt is capable of withstanding.

United States Patent Lawson [11] 3,783,704 Jan. 8, 1974 POWERTRANSMISSION, CONVEYOR AND VEHICLE TRACK [75] Inventor:

[73] Assignee: Dunlop Limited, London, England [22] Filed: Mar. 8, 197221 Appl. No.: 232,854

Neil Lawson, Glamorgan, Wales [30] Foreign Application Priority DataMar. 11, 1971 Great Britain 06,637/71 52 us. CI. .L 74/231 J 51 Int. CI..Fl6g 1/00 58 Field of Search .(74/231 R, 231 F,

[56] References Cited FOREIGN PATENTSOR APPLICATIONS 1,179,061 10/1964Germany .L 74/231 F 913,305 9/1946 France 74/231 R PrimaryExaminer-Leonard H. Gerin Attorney-Richard K. Stevens et al.

[57] ABSTRACT A belt having a joint with abutting ends both above andbelow the neutral axis of longitudinal bending of the belt, and aflexible jointing ply located between the abutting ends and lying alongthe neutral axis to reinforce the joint, the flexible jointing ply beingof a strength sufficient to withstand substantially the same tensileload as that which the uncut belt is capable of withstanding.

l6 Clailns, 6 Drawing Figures PATENTEDJAN 4 3,783,704

SHEEI 1 [IF 2 POWER TRANSMISSION, CONVEYOR AND VEHICLE TRACK Thisinvention relates to power transmission, conveyor and vehicle trackbelts and to methods of manufacturing joints in such belts.

There are already known many different types of belt joints and methodsof manufacturing them. These include lap joints, butt joints, hinged orplated joints and stepped joints.

While joints of these known types can be effective in regard to theirtensile strength under a direct steady pull, they tend to failunder theaction of repeated bending or under cyclically variable tensile loads.

In particular, increase or decrease of the bending modulus, from onetransverse section, at or near the joint, to another, causesconcentration of the bending stresses at the point of modulus changesince it becomes a"hinge point" and failure of the belt can rapidlyensue.

As regards failure under the action of cyclically variable tensile beltloads, these loads are concentrated, and thus the stress is increased atpoints where the tensile modulus changes and a resulting fatigue failurecan ensue if, at any belt section, the tensile modulus is below themodulus of the belt at points along the belt spaced apart from theregion of the joint.

It is an object of the present invention at least to reduce the adventof belt failure at or near to a belt joint compared with thepreviously-mentioned known joints.

According to one aspect of the present invention there is provided abelt having a joint with abutting ends both above and below the neutralaxis of longitudinal bending of the belt and a flexible jointing plylocated between the said abutting ends and lying along said neutral axisto reinforce the joint, said ply being of a strength sufficient towithstand substantially the same tensile load as that which the uncutbelt is capable of withstanding.

According to another aspect of the present invention the abutting endsof the joint are linear.

According to a further aspect of the present invention the abutting endsof the joint are non-linear, so that the line of the joint cannot lie inthe plane containing-the axis of bending of the belt.

In this instance, in particular, the non-linear ends can be of zig-zagor undulating configuration viewed in plan.

Particularly in instances where the abutting ends of the joint arelinear, the ends should be inclined to the longitudinal edges of thebelt and not disposed at right angles thereto; i.e., so that the line ofthe joint does not lie in the plane containing the axis of bending ofthe belt.

Where the abutting ends are inclined, the inclination of one pair ofabutting ends of the joint may be different from that of another suchpair.

The belt may be of elastomeric material and may have one or morereinforcing plies. One or more plies may be arranged above or below thejointing ply and neutral axis and they may be of woven or unwoventextile material, or steel material.

In another arrangement, the abutting ends above or below the jointingply may be staggered or offset relative to one another longitudinally ofthe belt when viewed in plan. Two, .three or more offsets may beincorporated at the joint dependent uponthe convenient division, and thequantity, of longitudinal belt reinforcing plies.

The material of the jointing ply may be of woven or unwoven textilematerial, for example, synthetic or natural fibers or filaments, or ofsteel filaments, and the textile or steel material may be twisted in theform of cords.

According to another aspect of the present invention a method of joiningbelt ends comprises laminating each belt end along the neutral axis ofbending of the belt associated with each end, inserting a jointing plybetween the laminated ends to extend along the said neutral axis to spanthe ends, butting the ends together and adhering the laminated ends,jointing ply and abutting ends together.

Preferably, in the case of a rubber-based belt, the adhesion is by meansof vulcanization and pressure, and in the case of a thermoplastic-basedbelt by means of heat and pressure.

According to a further aspect of the invention a method of joining beltends comprises severing the ends of the belt in an inclined direction tothe longitudinal direction of the belt when the ends are severedlinearly, or in an inclined or right-angle direction when the ends aresevered in a zig-zag or undulating direction, all as when viewed inplan, and all as described above in relation to the belt constructionitself as opposed to the method of making it.

Embodiments of the invention will now be described, by way of example,with reference to the accompanying sheets of drawings in which:

FIG. 1 shows a portion of belt, in longitudinal crosssection, to be cutand joined,

FIG. 2 shows in perspective a cut portion of the same belt,

FIG. 3 shows in perspective, the belt of FIG. 2 partly joined,

FIG. 4 shows, in longitudinal cross-section, the belt of FIG. 3completely joined by the method of the present invention,

FIG. 5 shows, in longitudinal cross-section, another belt joint formedin accordance with the present invention, and

FIG. 6 shows, in longitudinal cross-section, another belt joined inaccordance with the present invention.

In the construction shown in FIGS. 1 to 4, the two-ply belt 1, asillustrated in FIG. 1, is transversely severed, at the ends la and lb tobe jointed, so that, in plan view, a zig-Zag cut 2 is made, one cut endfitting snugly into the other cut end as shown in FIG. 2.

In FIG. 3 there is illustrated a lamination of the ends of the belt, thelamination being caused by a longitudinal cut 3, parallel with the beltsurface along .the neutral axis 6 of the belt. In this construction theneutral axis is mid-way between the reinforcing plies 4 and 5.

A part of the laminated belt, at each end to be joined, is lifted up asshown in FIG. 3 and a rubberized textile cord jointing ply 7 of astrength substantially equal to that of the uncut belt is located tospan the zig-zag cut 2 as shown in FIG. 4. The jointing ply is coatedwith a vulcanizable rubber solution as are also the surfaces of the beltwhich have been created by the laminating process.

The closed belt joined with the jointing ply sandwiched in position asshown in FIG. 4 is vulcanized toforma compact strong joint.

Fabric manufactured to the following specification is used for the pliesof the two-ply belt illustrated in the drawings.

Counts & Plies: Polyester Warp: made up from three yarns plied together,the resultant Tex count, after doubling, being 388.

Nylon Weft: made up from two yarns plied together, the resultant Texcount, after doubling, being 188.

Threads per inch:

Warp:30 Weft: l 5

WeavezPlain Breaking load Warp: l,l80 lb/inch (ravelled Weftz450 strip):

The jointing ply fabric would be woven to the following specification:

Counts & Plies:Polyester Warp: made up from six yarns plied together,the resultant Tex count, after doubling, being 675.

Nylon Weft: made up from four yarns plied together, the resultant Texcount, after doubling, being 382.

Threads per inch:

Warpz27 Weft:10.5

WeavezOxford Breaking load Warp: 2,150 lb/inch (ravelled Weft:650strip):

lt will be seen that the jointing ply fabric has approximately twice thetensile warp strength of the fabrics used in the body plies of the belt.

By virtue of this construction in which a zig-zag cut 2 is providedacross the width of the belt there is an avoidance of a transverse hingepoint at the cut.

By virtue of the provision of a jointing ply 7 located on the neutralaxis 6 of the belt, at the joint, the bending of the belt such as wouldoccur when passing over supporting or driving pulleys does not causehigh stresses in the jointing ply. The additional strength at the joint,apart from that provided by the jointing ply, contributed by thevulcanization of the butting zig-zag cut belt ends, adds considerablestrength to reduce the tendency of belt failure.

Moreover, by virtue of the fact that, in cross-section of the belt,there is provided ajointing ply having a tensile modulus at least equalto that conferred by the two reinforcing plies of the belt structure thedanger of the concentration of high stress leading to fatigue failure isreduced.

Whereas, in the preceding embodiment, as will be seen with reference toFIG. 4, the joints in the upper laminated part and the lower laminatedpart lie one above another in the alternative construction shown in FIG.5, they are offset one from another to form a staggered joint.

Although in the construction illustrated two-ply belts are shown, theinvention is applicable to belts without reinforcing plies or with anynumber of reinforcing plies and one or more jointing plies may beutilized located substantially on the neutral axis between the laminatedends of a belt to be joined.

FIG. 6 illustrates a staggered joint formed in a threeply belt ofnon-symmetrical construction. The reinforcing ply 8 is located in theplane of the neutral axis 9 between an upper reinforcement layer 10 andtwo lower reinforcement layers 11 and 12, and abutting ends both aboveand below the neutral axis are offset relative to each other.

In the case where there is already a ply at the neutral axis of bendingthis may be removed locally to make room for the reinforcing ply.

While in the embodiments described the belt is cut to form transverseslits in which the reinforcing ply is located, where it is required touse a reinforcing ply of substantial thickness and maintain a uniformbelt thickness, the belt may be cut so as to form a pair of trans versegrooves.

When the belt is utilized for a vehicle drive belt, e.g., for driving avehicle to be used in snow conditions, the belt may be provided withtransverse cleats or bars. The cleats or bars may be rivetted to thebelt and where a zig-zag joint is provided the cleat or bar can besecured in a position so that the rivets pass through some or all of thetoothed formations constituting the zigzag joint.

Having now described my invention, what I claim is:

1. A belt having ajoint comprising abutting ends both above and belowthe neutral axis of longitudinal bending of the belt, and a flexiblejointing ply of a tensile strength sufficient to withstand substantiallythe same tensile load as that which the uncut belt is capable ofwithstanding, said flexiblejointing ply being located between saidabutting ends and lying along said neutral axis.

2. A belt according to claim 1 wherein the abutting ends above theneutral axis are staggered relative to the abutting ends below theneutral axis.

3. A belt according to claim 1 wherein the abutting ends are linear.

4. A belt according to claim 3 wherein the abutting ends are inclinedrelative to the longitudinal edges of the belt.

5. A belt according to claim 4 wherein the abutting ends above and belowthe neutral axis are inclined at different angles relative to thelongitudinal edges of the belt.

6. A belt according to claim 1 wherein the abutting ends are of zig-zagconfiguration.

7. A belt according to claim 1 wherein the jointing ply is formed fromtextile material.

8. A belt according to claim 7 wherein the jointing ply is formed fromvulcanization textile material.

9. A belt according to claim 1 wherein the jointing ply comprises steelfilaments.

10. A belt according to claim 1 wherein one or more reinforcing pliesare provided.

11. A method of joining belt ends comprising laminating each belt endalong the neutral axis of bending of the belt, inserting a jointing plybetween the laminated ends to extend along the said netural axis tospand the ends, butting the ends together and adhereing the laminatedends, jointing ply and abutting ends together.

12. A method according to claim 11 wherein each belt end is laminated bycutting to form a transverse slit.

13. A method according to claim 11 wherein each belt end is laminated bycutting to form a transverse groove.

14. A method according to claim 11 wherein the belt ends arerubber-based and are joined together by vulcanization.

15. A method according to claim 11 wherein the belt ends arethermoplastic-based and are joined together by the application of heatand pressure.

16. In a belt having at least two reinforcement layers a jointcomprising a flexible jointing ply of a tensile strength sufficient towithstand substantially the same tensile load as the uncut belt, saidflexible jointing ply being located along the neutral axis andlongitudinally with a longitudinally extending neutral axis therebe- 5overlapping the abutting ends.

tween and abutting ends on said reinforcement layers,

1. A belt having a joint comprising abutting ends both above and belowthe neutral axis of longitudinal bending of the belt, and a flexiblejointing ply of a tensile strength sufficient to withstand substantiallythe same tensile load as that which the uncut belt is capable ofwithstanding, said flexible jointing ply being located between saidabutting ends and lying along said neutral axis.
 2. A belt according toclaim 1 wherein the abutting ends above the neutral axis are staggeredrelative to the abutting ends below the neutral axis.
 3. A beltaccording to claim 1 wherein the abutting ends are linear.
 4. A beltaccording to claim 3 wherein the abutting ends are inclined relative tothe longitudinal edges of the belt.
 5. A belt according to claim 4wherein the abutting ends above and beloW the neutral axis are inclinedat different angles relative to the longitudinal edges of the belt.
 6. Abelt according to claim 1 wherein the abutting ends are of zig-zagconfiguration.
 7. A belt according to claim 1 wherein the jointing plyis formed from textile material.
 8. A belt according to claim 7 whereinthe jointing ply is formed from vulcanization textile material.
 9. Abelt according to claim 1 wherein the jointing ply comprises steelfilaments.
 10. A belt according to claim 1 wherein one or morereinforcing plies are provided.
 11. A method of joining belt endscomprising laminating each belt end along the neutral axis of bending ofthe belt, inserting a jointing ply between the laminated ends to extendalong the said netural axis to spand the ends, butting the ends togetherand adhereing the laminated ends, jointing ply and abutting endstogether.
 12. A method according to claim 11 wherein each belt end islaminated by cutting to form a transverse slit.
 13. A method accordingto claim 11 wherein each belt end is laminated by cutting to form atransverse groove.
 14. A method according to claim 11 wherein the beltends are rubber-based and are joined together by vulcanization.
 15. Amethod according to claim 11 wherein the belt ends arethermoplastic-based and are joined together by the application of heatand pressure.
 16. In a belt having at least two reinforcement layerswith a longitudinally extending neutral axis therebetween and abuttingends on said reinforcement layers, a joint comprising a flexiblejointing ply of a tensile strength sufficient to withstand substantiallythe same tensile load as the uncut belt, said flexible jointing plybeing located along the neutral axis and longitudinally overlapping theabutting ends.